1. Field of the Invention
The present invention relates to wireless communications and, in, particular, to a method and apparatus for transmitting data in a wireless communication system.
2. Related Art
The next-generation multimedia wireless communication systems which are recently being actively researched are required to process and transmit various pieces of information, such as video and wireless data as well as the initial voice-centered services. The 4th generation wireless communication systems which are now being developed subsequently to the 3rd generation wireless communication systems are aiming at supporting high-speed data service of downlink 1 Gbps (gigabits per second) and uplink 500 Mbps (megabits per second). The object of the wireless communication system is to establish reliable communications between a number of users irrespective of their positions and mobility. However, a wireless channel has abnormal characteristics, such as path loss, noise, a fading phenomenon due to multi-path, inter-symbol interference (ISI), and the Doppler Effect resulting from the mobility of a user equipment. A variety of techniques are being developed in order to overcome the abnormal characteristics of the wireless channel and to increase the reliability of wireless communication.
Typically, a terminal in the existing system is connected to one of base stations for both an uplink and a downlink. In other words, the terminal is connected to the base station to perform uplink transmission to the base station and downlink reception from the base station. However, in some cases, situations in which a channel state of one of the uplink and the downlink may be worse or loads may be increased can occur. Accordingly, in these cases, the uplink transmission and downlink transmission can be considered to be performed by different base stations or nodes.
When the uplink transmission and downlink transmission are performed by different base stations or nodes, there is a need to propose a method for the efficient operations of the base station and terminal.